I'm feeling really stressed at the moment for a number of reasons, and I've completely gone off food.

I'm trying to eat properly but just can't make myself do it and feel physically sick if I try and force-feed myself.

I've eaten hardly anything for about a week. I had a sandwich yesterday (I tried to make myself eat both but gave up after one) and today I've had a grand total of one banana and a yoghurt. I havent been able to eat a proper meal for about a week, and I think that if I tried, I wouldnt be able to keep it down.
I know this isn't right but I'm not feeling ill at all. My problem is just that I can't eat.
Is it normal to go off food if you are stressed? I have had this before but it was fine the minute I felt happier. However this time it's going on for ages and I'm a bit worried I'm doing myself damage. My housemates have also noticed and are worried that I'm annorexic, despite me trying to explain that I'm not.